Cathode ray tube magnetic reproducer for video

ABSTRACT

An electron beam head for reproducing magnetically recorded video signals wherein magnetic fields from the record medium are channeled to the interior of the envelope to deflect the primary electrons transversely to the scanning direction of the beam. In one embodiment, the sensing electrodes are at opposite sides of the magnetic field region at an end wall of the envelope, while in another embodiment the primary electron beam passes through the openings in a grid of magnetic wires so as to interact with the magnetic fields therebetween, electrostatic deflecting means serving to deflect the electron beam through a substantial angle as it leaves the grid so as to impinge on sensing electrodes remote from the grid. In a third embodiment, secondary electrons are conducted into a branch tube extending from the main envelope and a single electrode senses the degree of deflection of the secondary electrons by the magnetic fields permeating the secondary emission region.

United States Patent [72] inventor Marvin Camras Glencoe,Ill. 211Appl.No. 350,514 22 Filed Ma -3,1964

Division of Ser. No. 832,848, Aug. 10, 1959, Patent No. 3,133,150 anddivision of Ser. No. 281,939,159 irw zt ia n N9, 299 43 451 PatentedTeBZ'iEffifi' [73] Assignee lit Research Institute Chicago, Ill.

[54] CATHODE RAY TUBE MAGNETIC REPRODUCER VIN-6 VIDRQ AMHJFIEI slsugu'ma man- W0 W0 MPuFrta lurur Primary Examiner-J. Russell GoudeauAttorney-Hill, Sherman, Meroni, Gross & Simpson ABSTRACT: An electronbeam head for reproducing magnetically recorded video signals whereinmagnetic fields from the record medium are channeled to the interior ofthe envelope to deflect the primary electrons transversely to thescanning direction of the beam. in one embodiment, the sensingelectrodes are at opposite sides of the magnetic field region at an endwall of the envelope, while in another embodiment the primary electronbeam passes through the openings in a grid of magnetic wires so as tointeract with the magnetic fields therebetween, electrostatic deflectingmeans serving to deflect the electron beam through a substantial angleas it leaves the grid so as to impinge on sensing electrodes remote fromthe grid. in a third embodiment, secondary electrons are conducted intoa branch tube extending from the main envelope and a single electrodesenses the degree of deflection of the secondary electrons by themagnetic fields permeating the secondary emission region.

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saw u 0F 4 INVENTOR Wary/n Ca mrczs w M w b ATTORNEY CATIIODE RAY TUBEMAGNETIC REPRODUCER FOR VIDEO The present application is a division ofmy earlier application Ser. No. 832,848 filed Aug. 10, 1959, now'U.S.Pat. No. 3,133,150 issued May 12, I965, which in turn is a division ofmy application Ser. No. 281,939 filed Apr. l l, 1952, now US. Pat. No.2,900,443 issued Aug. I8, 1959.

This invention relates to the reproduction of magnetically recordedsignals and particularly to the reproduction of video signals generatedby moving visual images.

One of the principal features and objects of the present invention isthe provision of a method and means for reproducing a recorded videosignal such as a television signal.

Another object of the present invention is to provide a novel method andmeans for translating a magnetic signal into an electrical signal.

A further object of the present invention is to provide a novel magneticreproducer head and a novel magnetized record for reproduction by saidhead.

Other objects and features which we believe to be characteristic of ourinvention are set forth with particularly in the appended claims. Ourinvention itself, however, both as to its organization, manner ofconstruction, and method of operation, together with further advantagesand objects thereof, may be best understood by reference to thefollowing description taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a diagrammatic showing of a video recording system and a videoreproducing system as they might be employed in recording and monitoringa video signal, and embodying the novel teachings and principals of thepresent invention;

FIG. 2 is a fragmentary diagrammatic plan view of a portion of a lengthymagnetizable medium magnetized in accordance with the novel teachingsandprinciples of the present invention;

FIG. 3 is a fragmentary diagrammatic showing of a lengthy magnetizablemedium magnetized in a second manner;

FIG. 4 is a fragmentary diagrammatic plan view of a lengthy magnetizablemedium magnetized in a third manner;

FIG. 5 is a fragmentary diagrammatic plan view of a lengthy magnetizahlemedium magnetized in a fourth manner;

FIG. 6 is a diagrammatic side view of an electromagnetic reproducer headembodying the novel teachings and principles of the present invention,and indicating an electric circuit for detecting the video signalproduced by the head;

FIG. 7 is an end elevational view of the reproducer head of FIG. 6looking from the right in FIG. 6 and with a portion of the lengthymagnetizable medium broken away;

FIG. 8 is a fragmentary horizontal sectional view of a reproducer headof FIG. 6;

FIG. 9 is a diagrammatic elevational view of a further form ofelectromagnetic reproducer head embodying the novel teachings andprinciples of the present invention;

FIG. 10 is a fragmentary front elevational view of the magnetic gridwire assembly of the head of FIG. 9;

FIG. 11 is a fragmentary cross-sectional view taken substantially alongthe line IX-IX of FIG. 10; 1

FIG. 12 is a diagrammatic side elevational view of a still further formof electromagnetic reproducer head embodying the novel teachings andprinciples of the present invention;

FIG. I3 is an end elevational view of the reproducer head of FIG. 12looking from the right in FIG. 12 and with a portion of the lengthymagnetizable medium broken away; and

FIG. 14 is a fragmentary enlarged vertical sectional view takensubstantially along the lines XIV-XIV in FIG. 13.

In FIG. I is illustrated the complete overall system of the presentinvention as it might be employed for example in recording a televisionprogram and contemporaneously reproducing the recording for purposes formonitoring. In such a case, the tape portions A,A' passing respectivelyover a recording head. B and reproducer headC could be part of the sametape. In any event, the tape portion A represents an elongatedmagnetizable medium which may bedelivered at a substantially uniformrate from a supply reel D and may first travel over an erase head E,then possibly a polarizing head F, and thereafter may travel over biashead G and the video electromagnetic recording head B and preferably anaudio electromagnetic recording head I. The tape portion A has a videosignal and preferably an audio signal recorded thereon and is passedover the video electromagnetic reproducer or playback head C and anaudio electromagnetic reproducer head K and is then wound on a takeupreel L at a substantially'uniform rate. The video reproducer head C isshown in detail in FIGS. 9, l0 and I1, and will be specificallydescribed hereinafter. The polarizing head F might be used inconjunction with a DC erase head E to depolarize the tape prior torecording thereon. The bias head G would likewise be used to aid indepolarizing the tape. If a high frequency erase head were used, thebias head would produce a high frequency bias field and the polarizinghead F would not be used. The bias field could be produced by therecording head B as will hereinafter be described. v

As indicated in FIG. 1, the video signal to be recorded may be suppliedto the video amplifier l, for example from a television receiver, orfrom television program lines, and the horizontal sweep generator 1 mayreceive a synchronizing signal from the same source. The audio input maybe supplied from the discriminator stage of a receiver or from audiolines to the audio amplifier 2 for the audio recording head I. A biasoscillator 2 may supply the bias field to the head I instead of using aseparate bias head. The electron gun control 3 is represented assupplying the recording tube filament, plate, and beam supply voltagesas well as control voltages for focus, positioning, intensity and thelike, while erase bias supply 4 furnishes erasing, polarizing and biasvoltages.

In the playback system, the video signal detected by reproducer head Cis delivered to the video amplifier 5 and the amplified signal controlsa conventional television picture tube P, for example. The videoamplifier may be provided with a conventional DC restorer circuit ifdesired. The output from the video amplifier 5 may be used tosynchronize the horizontal sweep generator 6 for the reproducer head Cand the deflection generators of the kinescope supply 7 for the picturetube P, or in some cases, as for example if the video signal is beingtransmitted, a master sync. generator can be used to synchronize thesweep generator 6 and deflection generators of the picture tube. Theaudio signal on the tape A is detected by the audio reproducer head Kand transmitted through audio amplifier 8 to the speaker S. Theelectrongun supply 9 is indicated as furnishing filament, plate and beam supplyvoltages for the playback tube C as well as control voltages for focus,positioning and the like.

The manner in which magnetization is impressed on a tape by the head Bof FIG. 1 is indicated diagrammatically in FIG. 2. Each horizontal sweepof a scanning beam in the head B produces a transverse line 111 ofmagnetization on the tape. This line 111 corresponds to a line of thevideo signal. If the video signal comprises a moving visual image whichis transmitted by scanning the image a number of times a second, amagnetic reproduction of that image will appear on the tape 110, thoughthe image might be elongated laterally or longitudinally, and eachcomplete scanning or frame of the moving image will have a magneticcounterpart in a frame 112 on the lengthy magnetizable medium 110. Infact, if magnetic particles were dusted on the film an actual imagecorresponding to the image of the video signal would appear at eachframe. The advantage of recording'the video signal line for line andframe for frame in this manner is that in reproduction, the tape neednot be scanned exactly line for line, but may be scanned between lines,or even longitudinally instead of transversely, that is the magneticimage need not be scanned in reproduction in the identical way in whichit was recorded.

In order to facilitate scanning of the recorded magnetic image, it isdesirable to have adjacent lines of the magnetic image overlap.Suchoverlapping can be accomplished, for example, by utilizing atransducer lamination in the head B of the thickness of 0.001 inch withthe tape travelling at the rate of IS inches per second.

With double interlaced scanning, two frames make each picture, but theabove cited advantages still hold, though not as perfectly as with aseries of complete pictures. Where it is practical to do so, it ispreferred to record complete rather than interlaced pictures. A recordhaving complete pictures can be converted to the interlaced type, byoffset heads, for example.

FIG. 3 illustrates a lengthy magnetizable medium 120 wherein three linesof a video signal 121, 122 and 123, for example, are located generallyin the same transverse row across the tape. For the same size tape, thisreduces the speed of scanning by a factor of three. Such a magneticrecording would be produced with the recording head of Fig. 1, if thebeam were moved across the target at one-third the scanning speed of thevideo signal being recorded. Each frame on the tape would then comprisethree transversely aligned frame portions 125, 126 and 127. In thiscase, while each frame portion could be scanned separately to reproducean image, such an image would not be satisfactory, since only one-thirdof the lines originally scanned are included in the image. A record ofthis type has the advantage of reduced scanning rate, by a factordepending on the number of columns. A slower scanning rate is importantwhen the system contains mechanical elements, or where inductivereactances, transmit time, etc. are problems.

In FIG. 4 is shown a record member similar to FIG. 2 in having a singleline of video signal across the width of the tape, but in which eachmagnetic line 130 on the tape is curved, as would be produced by thehead B of FIG. 1 if the transducer device were curved along itslongitudinal axis. The frames 131 are spaced serially along the tape asin FIG. 2. An are shaped path gives a longer line for a given tapewidth. This type of pattern is also an advantage when used with certainmechanical scanners.

In FIG. 5 each frame 135 comprises frame portions 136, 137 and 138 in anarcuate pattern across the tape.

Any one of the tapes illustrated in FIGS. 2 to 5 may be perforated atone edge as indicated at 140 in FIG. 3 for synchronizing the speed ofthe tape with the video signal, or a synchronizing control may beactuated by pickup from the magnetic frame pattern recorded on the tape;the control signals being amplified and used to correct for phase errorsof the tape with respect to the pickup head. An audio sound track mayrun along an edge of the tapes as indicated in FIG. 2 at 146.

In FIGS. 6, 7 and 8 is illustrated in electromagnetic reproducer headaccording to the present invention. The head comprises a cathode raytube 200 provided with an electrode assembly including an electronemitter 201 and accelerating and focusing electrodes such as 202 and 203producing an electron beam 206 having considerable vertical extent asindicated in FIG. 6. Such a beam will be termed a wide beam, widereferring to the vertical extent of the beam in the orientation of thetube illustrated. Horizontal deflection coils 204 and 205 areillustrated for sweeping the electron beam 206 back and forth across thetube end wall 208. A magnetic tape 210 having a video signal recorded onthe magnetizable coating thereof is moved across the exterior of the endwall. The tape may also have an audio signal indicated at 209 recordedat one edge thereof for reproduction by a conventional head. A similarsound track is indicated at 146 in FIG. 2. As indicated in FIGS. 7 and8, the head is preferably disposed within the tube end wall 208 asindicated in solid outline at 213a, or it may be located to one side at213b. It may also be located in advance of the head at 2136. With theaudio head in line with the video head as shown in 2130 or 213b, arecord tape is made which can readily be edited because picture andsound correspond.

The magnetic signal recorded on the tape is utilized to deflect the wideelectron beam 206. To this end a large number of high permeability wires214 are embedded in the end wall 208 of the tube. These wires areindicated diagrammatically only in FIGS. 6 and 8. There may be, forexample, 500 of them in a 2-inch tube wall, and they may be made of 4750alloy, which has the same coefficient of expansion as glass and thusmakes possible a good seal. As the tape passes the exterior ends of thewires, magnetic fields are set up through the wires which may extend asindicated'at 215 in FIG. 8. It will be observed that the fields extendgenerally in a horizontal plane between adjacent wires and generally atright angles to the beam. Thus the beam will be deflected eitherupwardly or downwardly depending on the polarity of the fields.Collector plates 217 and 218 are located above and below the wires tocollect the deflected electrons. The baffle plates 219 and 220accurately control the width'of the electron beam reaching the region ofthe collector plates regardless of small variations that usually occurin cathode ray tubes, and the magnetic fields 215 alter the proportionof the electrons traveling to each of the collector plates 217 and 218.

As indicated in FIG. 6, the output from collector plates 217 and 218 maybe delivered to the grids. of a pair of tubes 221 and 222 of thepush-pull amplifier by means of conductors 223 and 224. The video outputfrom the push-pull amplifier may be delivered to a video amplifier forfurther amplification. The elements at the face of the tube, andcoatings on the sides of the tube indicated at 226 in FIG. 8, arecharged posi' tive with respect to the electron gun, for focusing andacceleration. A low voltage beam is preferred because it allows greatersensitivity to deflection by the magnetic elements. Only one of thecollector elements 219 or 220 may be used with a single ended videoamplifier.

In FIGS. 9, 10 and 11 is illustrated a second embodiment of theelectromagnetic reproducer head of the present invention. This headcomprises a tube 230 providing a curved path for an electron beam 231.The beam is generated by an electron gun 233 and may be directed throughan elongated slit 234 in a baffle plate 236 by means of verticalpositioning plates 237 and 238 or by other suitable means. The beam isillustrated as being deflected downwardly to the target plates 239, 240by means of electrostatic deflecting plates 24], 242, however magneticdeflection means could be used advantageously. The horizontal sweepplates 243 cause the beam to cyclically travel across the length of thetarget plates 239, 240 which act similarly to target plates 217 and 218in FIG. 6. The reproducer head of FIG. 9 differs from that of FIG. 6 inthat the magnetic field of the record medium 245 is applied to the beamat a point remote from the target plates so that the effect of the fieldon the beam is amplified; that is, greater displacement of the beam atthe target plates is obtained for a given applied magnetic field.

The magnetic field of the tape 245 is applied to the beam by means of amagnetic grid 247 extending across the path of the beam 231. As shown inFIGS. 10 and 11, this grid comprises a plurality of vertically extendingmembers 249 of high permeability material which protrude through thetube wall 250 at the elbow 25] therein, FIG. 9. The wires are sealed inthe tube wall at the top and may project above the tube wall slightly asindicated in FIGS. 10 and 11 to receive the tape thereacross. The wiresmay be connected by a metallic nonmagnetic support bar 252 at theirlower ends and electrical connection may be made to the support bar 252to maintain it at a desired potential relative to the beam. As indicatedin FIG. 11, the beam passes between adjacent magnetic grid wires 249 andis deflected downwardly to a greater or lesser extent depending on thestrength of the magnetic field between the pair of grid wires 249through which the beam is momentarily passing. The beam may tend tospread somewhat as the target plates are approached, the proportion ofthe electrons reaching each plate depending on the signal on the tape245. It will be apparent that one target plate could be utilized whichwould receive varying amounts of electrons depending on the magneticsignal on the tape. A single ended output amplifier 255 may receive thesignal from the target plates.

in FIGS. l2, l3 and 14, a further form of electromagnetic reproducerhead according to the present invention is illustrated. The headcomprises a cathode ray tube 270 having a branch tube 271 for collectingsecondary emission electrons. The tape 272 having a magnetizable portionwith a video signal recorded thereon is passed across the end of thetube in a manner similar to that in recording. An electron gun 274supplies a stream of electrons 269 which is swept back and forth acrossthe end wall of the tube by means of horizontal deflectors 275. Verticaladjustment of the beam is afforded by vertical deflectors 276 which maybe used to initially adjust the beam vertically to impinge upon a slitor window 277, shown greatly enlarged in FIG. 14, in the end wall 273 ofthe tube. Baffle plates and a wide beam may be used to keep the beamaccurately on the slit surface, or alternatively automatic control ofthe deflection voltages may be used. The slit is preferably closed bymeans of an elongated horizontally extending strip 278 of nonmagneticconductive material, such as beryllium copper having base layer 279 ofsilver oxide and a coating 280 of caesium deposited'thereon. Sinceberyllium alone is a good secondary emitter, the other materials are notnecessary in all cases. The slit is preferably very narrow in order togive good resolution and the strip 278 very thin.

The reproduction is accomplished by moving the magnetized tape 272across the exterior surface of the strip 278 so that the magnetic fieldof successive transverse portions of the magnetized tape extends intothe interior of the tube to influence the secondary stream of electrons282 emitted progressively across the coating 280 of the strip 278 as thescanning beam 269 sweeps across the strip. An accelerating and focusingelectrode 283 directs the stream 282 to the video output collector 284,the electrode 283 preferably being shaped to give a linear gradientalong the length of the collector 284 corresponding to the gradientestablished along the length of the strip 278 by the magnetized tape.Video collector 284 may also be made to operate like elements 217 and218 in FIG. 6, but on the secondary instead of primary electron stream.Instead of the target 284, an electron multiplier may be provided togive an amplified video output. Thus the unmodulated scanning beam 269regulates the timing of the horizontal scanning stream 282 and themagnetized tape 272 operates to modulate the stream in accordance withthe video signal recorded on the tape. The target plate 284 may operateon a principle analogous to the plates 239 and 240 in FIG. 9 and asingle ended amplifier such as there shown may be utilized to amplifythe output from the plate 284.

The present application is a division of my earlier application Ser. No.832,848 filed Aug. 10, 1959 which in turn was a division of Ser. No. 28l ,939 filed Apr. ll, l952, now US. Pat. No. 2,900,443 issued Aug. 18,1959.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts ofthc presentinvention.

lclaim:

1. An electromagnetic reproducing head comprising a source of primaryelectrons, an elongated target, means for establishing a stream of saidprimary electrons from said source to said target, means for sweepingsaid stream of primary electrons across the length of said elongatedtarget, and means for channeling the magnetic fields of a lengthymagnetized medium traveling in close proximity to said target forinteraction between the magnetized medium and said stream of primaryelectrons, said target having means for collecting substantiallyexclusively said stream of primary electrons after means forelectrically detecting the effect of said medium on said beam of primaryelectrons, said target including a plurality of high permeability wiresspaced along the length of said target, and said detecting means beingadjacent said wires and collecting substantially exclusively said beamof primary electrons after interaction thereof with the magnetic fieldsdefined by said wires.

3. An electromagnetic reproducing head comprising a source of primaryelectrons, an elongated target, means for establishing a beam of saidprimary electrons from said source and cyclically sweeping across thelength of said target, means for accommodating a lengthy magnetizedmedium in close proximity to said target for interaction between themagnetic fields of said medium and said beam of primary electrons, andmeans for electrically detecting the effect of said medium on said beamof primary electrons, said electrically detecting means includingcollector plates on either side of said target, and in the path of thebeam of primary electrons for collecting substantially exclusively saidprimary electrons.

4. An electromagnetic reproducing head comprising a source of primaryelectrons, an elongated target, means for establishing a beam of saidprimary electrons from said source and cyclically sweeping across thelength of said target, means for accommodating a lengthy magnetizedmedium in close proximity to said target for interaction between themagnetic fields of said medium and said beam of primary electrons, andmeans for electrically detecting the effect of said medium on said beamof primary electrons, said target including a plurality of highpermeability wires spaced along the length of said target, and saidelectrically detecting means including collector plates on either sideof said target for collecting substantially exclusively said primaryelectrons to electrically reproduce the magnetized medium.

5. An electromagnetic reproducing head comprising a source of electrons,an elongated target, means for establishing a beam of electrons fromsaid source and cyclically sweeping across the length of said target,means for moving a lengthy magnetized medium in close proximity to saidtarget for interaction between the magnetic fields of said medium andsaid beam of electrons, and means for electrically detecting the effectof said medium on said beam, said electrically detecting means includingcollector plates on either side of said target, and said beam ofelectrons being of such width to impinge on said collector plates aswell as said target.

6. An electromagnetic reproducing head comprising a source of electrons,an elongated target, means for establishing a beam of electrons fromsaid source and cyclically sweeping across the length of said target,means for accommodating a lengthy magnetized medium in close proximityto said target for interaction between the magnetic fields of saidmedium and said beam of electrons, and means for electrically detectingthe effect of said medium on 'said beam, said electrically detectingmeans including collector plates on either side of said target, and saidbeam of electrons being of such width to impinge on said collectorplates as well as said target, and baffle plates limiting the width ofsaid beam reaching said collector plates.

7. An electromagnetic reproducing head comprising a source of electrons,an elongated target, means for establishing a beam of electrons fromsaid source and cyclically sweeping across the length of said target,means for moving a lengthy magnetized medium in close proximity to saidtarget for interaction between the magnetic fields of said medium andsaid beam of electrons, and means for electrically detecting the effectof said medium on said beam, said electrically detecting means includingcollector plates on either side of said target, and said beam ofelectrons being of such width to impinge on said collector plates aswell as said target, said target including a plurality of highpermeability wires spaced along the length of said target.

8. An electromagnetic reproducing head comprising a source of electrons,a target having secondary electron emission properties, means forestablishing a beam of electrons from said source to said target, meansfor establishing a stream of secondary electrons emitted from saidtarget, and means for accommodating a lengthy magnetized medium in closeproximity to said target for interaction between the magnetized mediumand said streams of electrons, characterized in that the establishingmeans for establishing said stream of secondary electrons directs saidstream of secondary electrons exclusively to one side of the beam ofelectrons from said source to said target, and an evacuated branch tubeextending from the target generally rearwardly at an acute anglerelative to the beam of electrons and having an electrode therein forcollecting said secondary electrons to electrically reproduce themagnetized medium.

9. An electromagnetic reproducing head comprising a source of primaryelectrons, an elongated target, means for establishing a beam of saidprimary electrons from said source and cyclically sweeping across thelength of said target, means for accommodating a lengthy magnetizedmedium in proximity to said beam of primary electrons for interactionbetween the magnetic fields of said medium and said beam of primaryelectrons, and means for electrically detecting substantiallyexclusively the effect of said medium on said beam of primary electronsto electrically reproduce the magnetized medium.

10 An electromagnetic reproducing head comprising a source of primaryelectrons, an elongated target, means for establishing a beam of saidprimary electrons from said source and cyclically sweeping across thelength of said target, means for accommodating a lengthy magnetizedmedium in proximity to said beam of primary electrons for interactionbetween the magnetic field of said medium and said beam of primaryelectrons, means for electrically detecting the effect of said medium onsaid beam of primary electrons, and means for channeling said magneticfields of said medium for interaction with said beam of primaryelectrons including a grid of high permeability members extending acrossthe path of said beam of primary electrons, said electrically detectingmeans being on the opposite side of the grid from said source andcollecting substantially exclusively said primary electrons andproviding an output signal in accordance with the interaction of themagnetic fields of said medium with said beam of primary electrons.

11. An electromagnetic reproducing head comprising a source ofelectrons, an elongated target, means for establishing a wide beam ofelectrons, of greater width than thickness, from said source andcyclicallysweeping across the length of said target, means forchanneling the magnetic fields on a lengthy magnetized medium forinteraction between the magnetic fields of said medium and said beam ofelectrons, and means for electrically detecting the effect of saidmagnetic fields on said beam, said establishing means comprising baffleplates extending parallel to the target at each side thereof with thebeam impinging on both of said baffle plates, and the portion of thebeam flowing between the baffle plates having said greater width thereofdetermined by the spacing of said baffle plates.

12. An electromagnetic reproducing head comprising a source ofelectrons, an elongated target, means for establishing a beam ofelectrons from said source and cyclically sweeping across the length ofsaid target to define an incident beam path, means for channeling themagnetic fields on a lengthy magnetized medium for interaction betweenthe magnetic fields of said medium and said beam of electrons at aregion of interaction, and means for electrically detecting the effectof said magnetic fields on said beam, said establishing means comprisingelectron beam intercepting means adjacent said target and upstreamthereof intercepting a portion of the beam to maintain the width of thebeam reaching said target substantially constant regardless of smallvariations in the path of the beam as it flows from said source towardsaid target, and said detecting means being on the side of saidintercepting means away from said source and receiving predominantlysaid beam ,of'electronics'as it travels along said incident beampath'after traversing said region of interaction.

13. An electromagnetic reproducing head comprising a source ofelectrons, an elongated target, means for establishing a beam ofelectrons from said source and cyclically sweeping across the lengthof-said target, means for channeling the magnetic field on a lengthymagnetized medium for interac tion between the magnetic fields of saidmedium and said beam for electrons, and means for electrically detectingthe effect of said magnetic fields on said beam, said channeling meanscomprising a grid of high permeability members with each memberextending generally parallel to each other and lying in a common planeand across the path of said beam with the beam sweeping in a planegenerally at right angles to said common plane of said members, saiddetecting means being on the side of said grid remote of said source anddirectly collecting said beamof electrons from said source and therebyproducing an electrical output signal in accordance with themagnetization of said medium.

14. The method of reproducing an electrical signal recorded magneticallyon a lengthy magnetizable medium, which comprises establishing a streamof primary electrons cyclically scanning an elongated region, andpassing said lengthy magnetizable medium adjacent said elongated regionto alter said scanning stream of primary electrons in accordance withthe magnetic record thereon, and collecting said primary electronssubstantially exclusively to generate an electrical output signal inaccordance with the signal recorded on the magnetizable medium.

15. A transducer mechanism comprising an elongated transducer devicehaving a plurality of magnetic circuits each with at least twononmagnetic gaps, means for accommodating an elongated magnetizablemedium across one of said gaps of each magnetic circuit, electronicstepping switch means utilizing primary electrons exclusively forsequentially linking with the other of said gaps of each magneticcircuit, and electric circuit means for conducting a video signaloperatively connected with said electronic stepping switch means forsequential linking with the other of said gaps of said transducerdevice, said magnetizable medium having a video signal recorded thereonfor linking said one gap of each magnetic circuit and for producing acorresponding magnetic field in said other of said gaps of each magneticcircuit, whereby said electric circuit means is energized with the videosignal recorded on said magnetizable medium.

16. An electromagnetic reproducing head comprising means forestablishing a stream of primary electrons, means for cyclicallydeflection said stream of primary electrons to establish an elongatedscanning region, means for channeling the magnetic fields on a lengthymagnetized medium for interaction with said stream of primary electronsin said scanning region, and means for detecting the effect of saidmagnetic fields on said stream of primary electrons substantiallyexclusively by collecting substantially only said primary electrons toproduce an electrical output signal in accordance with the magnetizationof said medium.

17. An apparatus for converting magnetic configurations to electricalsignals which comprises an envelope, means within said envelope forproducing a primary electron, beam, a target means sealed into apredetermined area of said envelope and positioned substantiallytransverse to said primary beam, said target means having a face, amagnetic condition space pattern record, said record being positioned sothat its magnetic fields permeate said target means and establish aspace pattern of magnetic fields on said face, means for subjectingconsecutive areas of said space pattern of magnetic fields to saidprimary beam whereby the electrons of said primary beam alter theirpaths in dependence on the magnetic condition of said space pattern offields, collecting means adapted for deriving signals substantiallyexclusively from said .electrons of said primary beam representative ofsaid space pattern of magnetic fields; and means for utilizing saidsignals.

18. In combination, a system comprising:

a. a magnetized elongated magnetic tape record medium having an activeexterior surface and having a record track of substantial length andwidth exhibiting a residual magnetization in a predetermined generaldirection in accordance with a recorded image, the residualmagnetization of said record track in accordance with said recordedimage producing external magnetic fields at said active exterior surfaceof said tape record medium varying in amplitude along the length of saidrecord track and varying in amplitude along the width of said recordtrack in accordance with said recorded image,

b. moving means for continuously moving said tape record medium atsubstantially a constant speed along a record medium path including arecord medium path region of limited longitudinal extent where saidactive exterior surface of said tape record medium conformssubstantially to a record medium path region plane over the entiretransverse extent of said record track,

c. an evacuated envelope having an evacuated interior and having recordmedium coupling means for receiving said active exterior surface of saidtape record medium in sliding contact therewith, said record mediumcoupling means transmitting the external magnetic fields of anincremental portion of the length of the record track to the interior ofsaid evacuated envelope, said incremental portion of the length of therecord track representing a line segment of said recorded image, and themagnetic fields from said line segment where they are of substantiallymaximum strength within the interior of the envelope lying predominantlyin a magnetic field region and in a transverse plane disposedsubstantially at right angles to said record medium path region planeand disposed transversely to the direction of movement of said recordmedium along said record medium path,

d. means comprising a source of primary electrons within said envelopefor supplying primary electrons and for directing said primary electronstoward and through said magnetic field region with the primary electronstraveling generally at right angles to the magnetic fields where theyare of substantially maximum strength within the interior of theenvelope as the primary electrons traverse said magnetic field region sothat the respective primary electrons are deflected in accordance withthe magnitude of said magnetic fields at the respective points oftraverse of said magnetic field region by the respective primaryelectrons,

e. means comprising an electrically conductive surface at the interiorof said envelope adjacent said magnetic field region which surface ismaintained at an electric potential to repel said primary electrons fortending to reverse the component of electron velocity which liessubstantially parallel to said transverse plane and substantiallyperpendicular to said record medium path region plane so that theprimary electrons move along respective incident electron paths withsaid velocity component thereof which is substantially parallel to saidtransverse plane being directed toward said magnetic field region, andmove along respective departing electron paths with said velocitycomponent thereof which is substantially parallel to said transverseplane being directed away from said magnetic field region,

f. cyclically operating deflection means for causing the primaryelectrons produced at successive instants of time in each cycle thereofto scan respective points along said magnetic field region and therebyto produce a sequential scanning of the incremental portion of thelength of said record track at said path region in said cycle, theduration of each cycle of said deflection means being sufficiently shortin relation to said speed of said record medium so that successive linesegments of the recorded image signal are scanned by said primaryelectrons during operation of said system.

g. collecting means in said envelope disposed for collecting saidprimary electrons after travel thereof through said magnetic fieldregion and providing an electrical output which is a function of thedeflection of said primary electrons by the magnetic fields of therecord medium at said magnetic field region, and said collecting meansin operation of said system providing a time varying electric signalcomprising a series of signal lines corresponding to successive linesegments of said recorded image on said magnetic tape record medium, and

h. said magnetic field region being relatively close to that portion ofthe exterior of said envelope which is occupied by the incrementallength of the record track being scanned at a given instant of time, incomparison to onehalf of each of the cross-sectional dimensions of saidenvelope, and'said magnetic coupling means extending from saidincremental length to said magnetic field region and being ofcorresponding relatively small dimension with respect to the directionsubstantially parallel to said transverse plane and substantiallyperpendicular to said record medium path region plane in comparison toone-half of each of the cross-sectional dimensions of said envelope.

19. An apparatus for converting magnetic configurations to electricalsignals which comprises:

a. an envelope,

b. a target comprising a conductive element having a face thereof withinsaid envelope,

c. means within said envelope for producing an electron beam,

01. Means for focusing, directing and accelerating said beam from saidbeam producing means to said target,

e. means for establishing a pattern of magnetic fields in proximity ofsaid face,

f. means for subjecting said beam to consecutive areas of said patternof magnetic fields so as to cause the electrons of said beam to altertheir paths in dependence on the magnetic condition of said pattern offields,

g. means for controlling the potential of said target, and

h. a circuit connected to said target for extracting electrical signalsderived by said target from said beam in representation of said patternof magnetic fields.

20. An apparatus for converting magnetic configurations to electricalsignals which comprises:

a. an envelope,

b. means within said envelope for producing an electron beam,

c. a target,

d. means for focusing and directing said beam from said beam producingmeans to said target,

e. means for positioning said beam relative to said target,

f. said target comprising means sealed into a predetermined area of saidenvelope having exterior surface means exterior to said envelope andhaving interior surface means within said envelope,

g1 means for disposing a magnetic space pattern record at the exteriorsurface means of said target in a manner to permeate said means sealedinto said predetermined area of said envelope and establish a spacepattern of magnetic fields on the interior surface means thereof,

h. means for subjecting consecutive areas of said space pattern to saidbeam to alter their paths in dependence on the magnetic condition ofsaid space pattern, and

i. said target comprising means for deriving signals from said beamrepresentative of said space pattern of magnetic fields.

21. An apparatus for converting magnetic configurations to electricalsignals which comprises:

a. an envelope,

b. means within said envelope for producing an electron beam,

c. a target,

d. means for focusing and directing said beam from said beam producingmeans to said target,

e. means for positioning said beam relative to said target,

f. said target comprising means sealed into a predetermined area of saidenvelope and having exterior surface means at the exterior of saidenvelope and having interior surface means at the interior of saidenvelope,

. means for disposing a magnetic space pattern record at the exteriorsurface means of said target in a manner to permeate said means sealedinto said predetermined area of said envelope and establish a spacepattern of magnetic fields on the interior surface means thereof,

h. said focusing and directing means including means for acceleratingsaid beam to the region of said space pattern of magnetic fields,

'. means for subjecting consecutive areas of said space pattern ofmagnetic fields to said beam so as to cause the electrons of said beamto alter their paths in dependence on the magnetic condition of saidspace pattern of fields,

j. means for providing a low voltage beam in the proximity of saidinterior surface means of said target, and

it. said target comprising means for deriving electrical signals fromsaid beam representative of said space pattern of magnetic fields.

22. An apparatus for converting magnetic configurations to electricalsignals comprising:

beam producing means to said target means,

b. means for subjecting consecutive areas of said space pattern ofmagnetic fields to said beam so as to cause the electrons of said beamto alter their paths in dependence on the magnetic condition of saidspace pattern of fields, and 4 i. said target means comprising means forderiving signals from said beam in representation of said space patternof magnetic fields.

23. An apparatus for converting magnetic configurations to electricalsignals which comprises:

a. an envelope,

b. a target means comprising a conductive element having a face thereof,within said envelope,

c. means within said envelope for producing an electron beam,

d. means for focusing and directing said beam from said beam producingmeans to said target means,

e. means for establishing a pattern of magnetic fields in a region ofsaid face,

f. means for subjecting said beam to said pattern of magnetic fields soas to cause the electrons of said beam to alter their paths independence on the magnetic condition of said pattern of fields,

g. said face being at a potential to reject said beam in a manner toprevent, substantially, said beam from landing on said face,

h. an electrode positioned away from said face and at a potential toattract said beam in a generally reverse direction, and

i. means for extracting electrical signals from said beam inrepresentation of said pattern of magnetic fields.

1. An electromagnetic reproducing head comprising a source of primaryelectrons, an elongated target, means for establishing a stream of saidprimary electrons from said source to said target, means for sweepingsaid stream of primary electrons across the length of said elongatedtarget, and means for channeling the magnetic fields of a lengthymagnetized medium traveling in close proximity to said target forinteraction between the magnetized medium and said stream of primaryelectrons, said target having means for collecting substantiallyexclusively said stream of primary electrons after interaction thereofwith said magnetized medium to generate an electric output signal inaccordance with said interaction.
 2. An electromagnetic reproducing headcomprising a source of primary electrons, an elongated target, means forestablishing a beam of primary electrons from said source and cyclicallysweeping across the length of said target, means for accommodating alengthy magnetized medium in close proximity to said target forinteraction between the magnetic fields of said medium and said beam ofprimary electrons, and means for electrically detecting the effect ofsaid medium on said beam of primary electrons, said target including aplurality of high permeability wires spaced along the length of saidtarget, and said detecting means being adjacent said wires andcollecting substantially exclusively said beam of primary electronsafter interaction thereof with the magnetic fields defined by saidwires.
 3. An electromagnetic reproducing head comprising a source ofprimary electrons, an elongated target, means for establishing a beam ofsaid primary electrons from said source and cyclically sweeping acrossthe length of said target, means for accommodating a lengthy magnetizedmedium in close proximity to said target for interaction between themagnetic fields of said medium and said beam of primary electrons, andmeans for electrically detecting the effect of said medium on said beamof primary electrons, said electrically detecting means includingcollector plates on either side Of said target, and in the path of thebeam of primary electrons for collecting substantially exclusively saidprimary electrons.
 4. An electromagnetic reproducing head comprising asource of primary electrons, an elongated target, means for establishinga beam of said primary electrons from said source and cyclicallysweeping across the length of said target, means for accommodating alengthy magnetized medium in close proximity to said target forinteraction between the magnetic fields of said medium and said beam ofprimary electrons, and means for electrically detecting the effect ofsaid medium on said beam of primary electrons, said target including aplurality of high permeability wires spaced along the length of saidtarget, and said electrically detecting means including collector plateson either side of said target for collecting substantially exclusivelysaid primary electrons to electrically reproduce the magnetized medium.5. An electromagnetic reproducing head comprising a source of electrons,an elongated target, means for establishing a beam of electrons fromsaid source and cyclically sweeping across the length of said target,means for moving a lengthy magnetized medium in close proximity to saidtarget for interaction between the magnetic fields of said medium andsaid beam of electrons, and means for electrically detecting the effectof said medium on said beam, said electrically detecting means includingcollector plates on either side of said target, and said beam ofelectrons being of such width to impinge on said collector plates aswell as said target.
 6. An electromagnetic reproducing head comprising asource of electrons, an elongated target, means for establishing a beamof electrons from said source and cyclically sweeping across the lengthof said target, means for accommodating a lengthy magnetized medium inclose proximity to said target for interaction between the magneticfields of said medium and said beam of electrons, and means forelectrically detecting the effect of said medium on said beam, saidelectrically detecting means including collector plates on either sideof said target, and said beam of electrons being of such width toimpinge on said collector plates as well as said target, and baffleplates limiting the width of said beam reaching said collector plates.7. An electromagnetic reproducing head comprising a source of electrons,an elongated target, means for establishing a beam of electrons fromsaid source and cyclically sweeping across the length of said target,means for moving a lengthy magnetized medium in close proximity to saidtarget for interaction between the magnetic fields of said medium andsaid beam of electrons, and means for electrically detecting the effectof said medium on said beam, said electrically detecting means includingcollector plates on either side of said target, and said beam ofelectrons being of such width to impinge on said collector plates aswell as said target, said target including a plurality of highpermeability wires spaced along the length of said target.
 8. Anelectromagnetic reproducing head comprising a source of electrons, atarget having secondary electron emission properties, means forestablishing a beam of electrons from said source to said target, meansfor establishing a stream of secondary electrons emitted from saidtarget, and means for accommodating a lengthy magnetized medium in closeproximity to said target for interaction between the magnetized mediumand said streams of electrons, characterized in that the establishingmeans for establishing said stream of secondary electrons directs saidstream of secondary electrons exclusively to one side of the beam ofelectrons from said source to said target, and an evacuated branch tubeextending from the target generally rearwardly at an acute anglerelative to the beam of electrons and having an electrode therein forcollecting said secondary electrons to electrically reproduce themagnetized medium.
 9. AN electromagnetic reproducing head comprising asource of primary electrons, an elongated target, means for establishinga beam of said primary electrons from said source and cyclicallysweeping across the length of said target, means for accommodating alengthy magnetized medium in proximity to said beam of primary electronsfor interaction between the magnetic fields of said medium and said beamof primary electrons, and means for electrically detecting substantiallyexclusively the effect of said medium on said beam of primary electronsto electrically reproduce the magnetized medium. 10 An electromagneticreproducing head comprising a source of primary electrons, an elongatedtarget, means for establishing a beam of said primary electrons fromsaid source and cyclically sweeping across the length of said target,means for accommodating a lengthy magnetized medium in proximity to saidbeam of primary electrons for interaction between the magnetic field ofsaid medium and said beam of primary electrons, means for electricallydetecting the effect of said medium on said beam of primary electrons,and means for channeling said magnetic fields of said medium forinteraction with said beam of primary electrons including a grid of highpermeability members extending across the path of said beam of primaryelectrons, said electrically detecting means being on the opposite sideof the grid from said source and collecting substantially exclusivelysaid primary electrons and providing an output signal in accordance withthe interaction of the magnetic fields of said medium with said beam ofprimary electrons.
 11. An electromagnetic reproducing head comprising asource of electrons, an elongated target, means for establishing a widebeam of electrons, of greater width than thickness, from said source andcyclically sweeping across the length of said target, means forchanneling the magnetic fields on a lengthy magnetized medium forinteraction between the magnetic fields of said medium and said beam ofelectrons, and means for electrically detecting the effect of saidmagnetic fields on said beam, said establishing means comprising baffleplates extending parallel to the target at each side thereof with thebeam impinging on both of said baffle plates, and the portion of thebeam flowing between the baffle plates having said greater width thereofdetermined by the spacing of said baffle plates.
 12. An electromagneticreproducing head comprising a source of electrons, an elongated target,means for establishing a beam of electrons from said source andcyclically sweeping across the length of said target to define anincident beam path, means for channeling the magnetic fields on alengthy magnetized medium for interaction between the magnetic fields ofsaid medium and said beam of electrons at a region of interaction, andmeans for electrically detecting the effect of said magnetic fields onsaid beam, said establishing means comprising electron beam interceptingmeans adjacent said target and upstream thereof intercepting a portionof the beam to maintain the width of the beam reaching said targetsubstantially constant regardless of small variations in the path of thebeam as it flows from said source toward said target, and said detectingmeans being on the side of said intercepting means away from said sourceand receiving predominantly said beam of electronics as it travels alongsaid incident beam path after traversing said region of interaction. 13.An electromagnetic reproducing head comprising a source of electrons, anelongated target, means for establishing a beam of electrons from saidsource and cyclically sweeping across the length of said target, meansfor channeling the magnetic field on a lengthy magnetized medium forinteraction between the magnetic fields of said medium and said beam forelectrons, and means for electrically detecting the effect of saidmagnetic fields on said beam, said channeling means comprising a grid ofhigh permeability members with each member extending generally parallelto each other and lying in a common plane and across the path of saidbeam with the beam sweeping in a plane generally at right angles to saidcommon plane of said members, said detecting means being on the side ofsaid grid remote of said source and directly collecting said beam ofelectrons from said source and thereby producing an electrical outputsignal in accordance with the magnetization of said medium.
 14. Themethod of reproducing an electrical signal recorded magnetically on alengthy magnetizable medium, which comprises establishing a stream ofprimary electrons cyclically scanning an elongated region, and passingsaid lengthy magnetizable medium adjacent said elongated region to altersaid scanning stream of primary electrons in accordance with themagnetic record thereon, and collecting said primary electronssubstantially exclusively to generate an electrical output signal inaccordance with the signal recorded on the magnetizable medium.
 15. Atransducer mechanism comprising an elongated transducer device having aplurality of magnetic circuits each with at least two nonmagnetic gaps,means for accommodating an elongated magnetizable medium across one ofsaid gaps of each magnetic circuit, electronic stepping switch meansutilizing primary electrons exclusively for sequentially linking withthe other of said gaps of each magnetic circuit, and electric circuitmeans for conducting a video signal operatively connected with saidelectronic stepping switch means for sequential linking with the otherof said gaps of said transducer device, said magnetizable medium havinga video signal recorded thereon for linking said one gap of eachmagnetic circuit and for producing a corresponding magnetic field insaid other of said gaps of each magnetic circuit, whereby said electriccircuit means is energized with the video signal recorded on saidmagnetizable medium.
 16. An electromagnetic reproducing head comprisingmeans for establishing a stream of primary electrons, means forcyclically deflection said stream of primary electrons to establish anelongated scanning region, means for channeling the magnetic fields on alengthy magnetized medium for interaction with said stream of primaryelectrons in said scanning region, and means for detecting the effect ofsaid magnetic fields on said stream of primary electrons substantiallyexclusively by collecting substantially only said primary electrons toproduce an electrical output signal in accordance with the magnetizationof said medium.
 17. An apparatus for converting magnetic configurationsto electrical signals which comprises an envelope, means within saidenvelope for producing a primary electron beam, a target means sealedinto a predetermined area of said envelope and positioned substantiallytransverse to said primary beam, said target means having a face, amagnetic condition space pattern record, said record being positioned sothat its magnetic fields permeate said target means and establish aspace pattern of magnetic fields on said face, means for subjectingconsecutive areas of said space pattern of magnetic fields to saidprimary beam whereby the electrons of said primary beam alter theirpaths in dependence on the magnetic condition of said space pattern offields, collecting means adapted for deriving signals substantiallyexclusively from said electrons of said primary beam representative ofsaid space pattern of magnetic fields; and means for utilizing saidsignals.
 18. In combination, a system comprising: a. a magnetizedelongated magnetic tape record medium having an active exterior surfaceand having a record track of substantial length and width exhibiting aresidual magnetization in a predetermined general direction inaccordance with a recorded image, the residual magnetization of saidrecord track in accordance with said recorded image producing externalmagnetic fields at said active exterior surface of said tape recordmedium varying in amplitude along the length of said record track andvarying in amplitude along the width of said record track in accordancewith said recorded image, b. moving means for continuously moving saidtape record medium at substantially a constant speed along a recordmedium path including a record medium path region of limitedlongitudinal extent where said active exterior surface of said taperecord medium conforms substantially to a record medium path regionplane over the entire transverse extent of said record track, c. anevacuated envelope having an evacuated interior and having record mediumcoupling means for receiving said active exterior surface of said taperecord medium in sliding contact therewith, said record medium couplingmeans transmitting the external magnetic fields of an incrementalportion of the length of the record track to the interior of saidevacuated envelope, said incremental portion of the length of the recordtrack representing a line segment of said recorded image, and themagnetic fields from said line segment where they are of substantiallymaximum strength within the interior of the envelope lying predominantlyin a magnetic field region and in a transverse plane disposedsubstantially at right angles to said record medium path region planeand disposed transversely to the direction of movement of said recordmedium along said record medium path, d. means comprising a source ofprimary electrons within said envelope for supplying primary electronsand for directing said primary electrons toward and through saidmagnetic field region with the primary electrons traveling generally atright angles to the magnetic fields where they are of substantiallymaximum strength within the interior of the envelope as the primaryelectrons traverse said magnetic field region so that the respectiveprimary electrons are deflected in accordance with the magnitude of saidmagnetic fields at the respective points of traverse of said magneticfield region by the respective primary electrons, e. means comprising anelectrically conductive surface at the interior of said envelopeadjacent said magnetic field region which surface is maintained at anelectric potential to repel said primary electrons for tending toreverse the component of electron velocity which lies substantiallyparallel to said transverse plane and substantially perpendicular tosaid record medium path region plane so that the primary electrons movealong respective incident electron paths with said velocity componentthereof which is substantially parallel to said transverse plane beingdirected toward said magnetic field region, and move along respectivedeparting electron paths with said velocity component thereof which issubstantially parallel to said transverse plane being directed away fromsaid magnetic field region, f. cyclically operating deflection means forcausing the primary electrons produced at successive instants of time ineach cycle thereof to scan respective points along said magnetic fieldregion and thereby to produce a sequential scanning of the incrementalportion of the length of said record track at said path region in saidcycle, the duration of each cycle of said deflection means beingsufficiently short in relation to said speed of said record medium sothat successive line segments of the recorded image signal are scannedby said primary electrons during operation of said system, g. collectingmeans in said envelope disposed for collecting said primary electronsafter travel thereof through said magnetic field region and providing anelectrical output which is a function of the deflection of said primaryelectrons by the magnetic fields of the record medium at said magneticfield region, and said collecting means in operation of said systemproviding a time varying electric signal comprising a series of signallines corresponding to successive line segments of said recorded imageon said magnetic tape record medium, and h. said maGnetic field regionbeing relatively close to that portion of the exterior of said envelopewhich is occupied by the incremental length of the record track beingscanned at a given instant of time, in comparison to one-half of each ofthe cross-sectional dimensions of said envelope, and said magneticcoupling means extending from said incremental length to said magneticfield region and being of corresponding relatively small dimension withrespect to the direction substantially parallel to said transverse planeand substantially perpendicular to said record medium path region planein comparison to one-half of each of the cross-sectional dimensions ofsaid envelope.
 19. An apparatus for converting magnetic configurationsto electrical signals which comprises: a. an envelope, b. a targetcomprising a conductive element having a face thereof within saidenvelope, c. means within said envelope for producing an electron beam,d. Means for focusing, directing and accelerating said beam from saidbeam producing means to said target, e. means for establishing a patternof magnetic fields in proximity of said face, f. means for subjectingsaid beam to consecutive areas of said pattern of magnetic fields so asto cause the electrons of said beam to alter their paths in dependenceon the magnetic condition of said pattern of fields, g. means forcontrolling the potential of said target, and h. a circuit connected tosaid target for extracting electrical signals derived by said targetfrom said beam in representation of said pattern of magnetic fields. 20.An apparatus for converting magnetic configurations to electricalsignals which comprises: a. an envelope, b. means within said envelopefor producing an electron beam, c. a target, d. means for focusing anddirecting said beam from said beam producing means to said target, e.means for positioning said beam relative to said target, f. said targetcomprising means sealed into a predetermined area of said envelopehaving exterior surface means exterior to said envelope and havinginterior surface means within said envelope, g. means for disposing amagnetic space pattern record at the exterior surface means of saidtarget in a manner to permeate said means sealed into said predeterminedarea of said envelope and establish a space pattern of magnetic fieldson the interior surface means thereof, h. means for subjectingconsecutive areas of said space pattern to said beam to alter theirpaths in dependence on the magnetic condition of said space pattern, andi. said target comprising means for deriving signals from said beamrepresentative of said space pattern of magnetic fields.
 21. Anapparatus for converting magnetic configurations to electrical signalswhich comprises: a. an envelope, b. means within said envelope forproducing an electron beam, c. a target, d. means for focusing anddirecting said beam from said beam producing means to said target, e.means for positioning said beam relative to said target, f. said targetcomprising means sealed into a predetermined area of said envelope andhaving exterior surface means at the exterior of said envelope andhaving interior surface means at the interior of said envelope, g. meansfor disposing a magnetic space pattern record at the exterior surfacemeans of said target in a manner to permeate said means sealed into saidpredetermined area of said envelope and establish a space pattern ofmagnetic fields on the interior surface means thereof, h. said focusingand directing means including means for accelerating said beam to theregion of said space pattern of magnetic fields, i. means for subjectingconsecutive areas of said space pattern of magnetic fields to said beamso as to cause the electrons of said beam to alter their paths independence on the magnetic condition of said space pattern of fields, j.means for providing a low voltage beam in the proximity of said interiorsurface means of said target, and k. said target comprising means forderiving electrical signals from said beam representative of said spacepattern of magnetic fields.
 22. An apparatus for converting magneticconfigurations to electrical signals comprising: a. an envelope having asubstantially zero electrical conductivity, b. said envelope having anend wall, c. a target means, d. said target means comprising aconductive layer on the interior face of said end wall, e. means fordisposing a magnetic condition space pattern record at the exterior ofsaid end wall in a manner to permeate and establish a space pattern ofmagnetic fields on said target means, f. means within said envelope forproducing an electron beam, g. means for focusing and directing saidbeam from said beam producing means to said target means, h. means forsubjecting consecutive areas of said space pattern of magnetic fields tosaid beam so as to cause the electrons of said beam to alter their pathsin dependence on the magnetic condition of said space pattern of fields,and i. said target means comprising means for deriving signals from saidbeam in representation of said space pattern of magnetic fields.
 23. Anapparatus for converting magnetic configurations to electrical signalswhich comprises: a. an envelope, b. a target means comprising aconductive element having a face thereof within said envelope, c. meanswithin said envelope for producing an electron beam, d. means forfocusing and directing said beam from said beam producing means to saidtarget means, e. means for establishing a pattern of magnetic fields ina region of said face, f. means for subjecting said beam to said patternof magnetic fields so as to cause the electrons of said beam to altertheir paths in dependence on the magnetic condition of said pattern offields, g. said face being at a potential to reject said beam in amanner to prevent, substantially, said beam from landing on said face,h. an electrode positioned away from said face and at a potential toattract said beam in a generally reverse direction, and i. means forextracting electrical signals from said beam in representation of saidpattern of magnetic fields.